In numerous circumstances it is necessary to grip and raise pipes and cylindrical objects with their axes being vertically oriented, the objects being of great weight, for transporting them and locating them at the desired site.
An example of such an operation is the construction of extraction wells, in which a number of drill pipes are to be positioned in succession, or the positioning of foundation on piles and the like, as in the case of marine platforms for petroleum extraction.
In all the cases, it is essential to provide a reliable gripping of the cylindrical object, which demands the clamping of the object with high force, and checking of the descent and supporting the weight of the object by friction.
A clamp or chuck must therefore be provided, which is equipped with means for developing such clamping force and which shall be capable, for its part, of being lifted and transported according to the requirements of the envisaged use.
In particular, in the case of marine platforms, it is necessary to position foundation piles or tubes of great length. In this case in many common applications, a number of segments of tubes having a maximum convenient length, which nevertheless is insufficient for forming a foundation pile in one single piece, must be connected together on the jobsite by welding or by the use of joints of other types, which are not always perfect, with complex operations in order to obtain the piles of the complete length required.
To overcome these problems it is possible to prepare in the contractor's yard the piles of the required length, by joining together a plurality of tube segments, the joining being carried out by welding or other means, under appropriate conditions, and then transporting the already prepared piles to their location zone on the platform and positioning them in their seat.
For this procedure, however, gripping devices are required that are capable of raising and supporting tubular objects of extremely large dimensions and high weights, causing very high mechanical loadings in the lifting devices, where moreover the tubular objects may possess geometrical irregularities, such as an oval configuration or the like, which may render gripping them difficult.